Molten steel pouring nozzle

Abstract

A molten steel pouring nozzle which comprises: a nozzle body comprising an alumina-graphite refractory, having, along the axis thereof, a bore through which molten steel flows; and an outer refractory layer arranged on an outside portion of the nozzle body so as to be integral with the nozzle body and to be flush with an outer surface thereof, the outer refractory layer being arranged on a portion of the outside portion of the nozzle body, which portion is in contact, when a lower portion of the molten steel pouring nozzle is immersed into molten steel, with the open air without being immersed into the molten steel, and the outer refractory layer consisting essentially of: -alumina (Al2O3) from 40 to 75 wt. %, -carbon (C) from 10 to 30 wt. %, -silica (SiO2) from 1 to 30 wt. %, -silicon carbide (SiC) from 1 to 20 wt. %, -and -low-melting glass from 1 to 10 wt. %. -

What is claimed is: 
     
       1. A molten steel pouring nozzle which comprises: a nozzle body comprising an alumina-graphite refractory, having, along the axis thereof, a bore through which molten steel flows; and   an outer refractory layer arranged on an outside portion of said nozzle body so as to be integral with said nozzle body and to be flush with an outer surface thereof, said outer refractory layer being arranged on a portion of said outside portion of said nozzle body, which portion is in contact, when a lower portion of said molten steel pouring nozzle is immersed into molten steel, with the open air without being immersed into said molten steel, and said outer refractory layer consisting essentially of:   ______________________________________                                    
alumina (Al.sub.2 O.sub.3)                                                
                from 40 to 75                                             
                             wt. %                                        
carbon (C)      from 10 to 30                                             
                             wt. %,                                       
silica (SiO.sub.2)                                                        
                from  1 to 30                                             
                             wt. %,                                       
silicon carbide (SiC)                                                     
                from  1 to 20                                             
                             wt. %,                                       
and                                                                       
low-melting glass                                                         
                from  1 to 10                                             
                             wt. %; and                                   
said low-melting glass consisting essentially of:                         
alumina (Al.sub.2 O.sub.3)                                                
                from  1.5 to wt. %,                                       
silica (SiO.sub.2)                                                        
                from 20.0 to 56.0                                         
                             wt. %,                                       
calcium oxide (CaO)                                                       
                from  2.5 to 14.4                                         
                             wt. %,                                       
magnesia (MgO)  from 0.05 to 1.60                                         
                             wt. %,                                       
potassium oxide (K.sub.2 O)                                               
                from 0.25 to 6.40                                         
                             wt. %,                                       
sodium oxide (Na.sub.2 O)                                                 
                from  0.5 to wt. %,                                       
boric acid (B.sub.2 O.sub.3)                                              
                from  2.5 to 24.0                                         
                             wt. %,                                       
and                                                                       
boron carbide (B.sub.4 C)                                                 
                from 20.0 to 50.0                                         
                             wt. %.                                       
______________________________________                                    
       
     
     
       2. A molten steel pouring nozzle as claimed in claim 1, wherein: said outer refractory layer of said molten steel pouring nozzle has a thickness within a range of from 1 to 15 mm.   
     
     
       3. A molten steel pouring nozzle as claimed in claim 2, wherein the outer refractory layer consists essentially of 49.2 wt. % alumina, 19.4 wt. % carbon, 19.8 wt. % silica, 9.8 wt. % silicon carbide and 1.8 wt. % low-melting glass. 
     
     
       4. A molten steel pouring nozzle as claimed in claim 2, wherein the outer refractory layer consists essentially of 49.2 wt. % alumina, 19.4 wt. % carbon, 18.8 wt. % silica, 8.1 wt. % silicon carbide and 3.7 wt. % low-melting glass. 
     
     
       5. A molten steel pouring nozzle as claimed in claim 2, wherein the outer refractory layer consists essentially of 49.2 wt. % alumina, 19.4 wt. % carbon, 17.4 wt. % silica, 7.5 wt. % silicon carbide and 6.5 wt. % low-melting glass. 
     
     
       6. A molten steel pouring nozzle as claimed in claim 2, wherein the outer refractory layer consists essentially of 49.2 wt. % alumina, 19.4 wt. % carbon, 16.0 wt. % silica, 6.1 wt. % silicon carbide and 9.3 wt. % low-melting glass. 
     
     
       7. A molten steel pouring nozzle as claimed in claim 2, wherein the low-melting glass consists essentially of 3.1 wt. % alumina, 37.1 wt. % silica, 5.5 wt. % calcium oxide, 0.7 wt. % magnesia, 1.3 wt. % potassium oxide, 4.6 wt. % sodium oxide, 14.4 wt. % boric acid and 33.3 wt. % boron carbide. 
     
     
       8. A molten steel pouring nozzle as claimed in claim 3, wherein the low-melting glass consists essentially of 3.1 wt. % alumina, 37.1 wt. % silica, 5.5 wt. % calcium oxide, 0.7 wt. % magnesia, 1.3 wt. % potassium oxide, 4.6 wt. % sodium oxide, 14.4 wt. % boric acid and 33.3 wt. % boron carbide. 
     
     
       9. A molten steel pouring nozzle as claimed in claim 4, wherein the low-melting glass consists essentially of 3.1 wt. % alumina, 37.1 wt. % silica, 5.5 wt. % calcium oxide, 0.7 wt. % magnesia, 1.3 wt. % potassium oxide, 4.6 wt. % sodium oxide, 14.4 wt. % boric acid and 33.3 wt. % boron carbide. 
     
     
       10. A molten steel pouring nozzle as claimed in claim 5, wherein the low-melting glass consists essentially of 3.1 wt. % alumina, 37.1 wt. % silica, 5.5 wt. % calcium oxide, 0.7 wt. % magnesia, 1.3 wt. % potassium oxide, 4.6 wt. % sodium oxide, 14.4 wt. % boric acid and 33.3 wt. % boron carbide. 
     
     
       11. A molten steel pouring nozzle as claimed in claim 6, wherein the low-melting glass consists essentially of 3.1 wt. % alumina, 37.1 wt. % silica, 5.5 wt. % calcium oxide, 0.7 wt. % magnesia, 1.3 wt. % potassium oxide, 4.6 wt. % sodium oxide, 14.4 wt. % boric acid and 33.3 wt. % boron carbide.